Plaster board



Oct. 13, 1925 M. K. ARMSTRONG PLAsTER BOARD Filed oen-1.' 192;

PatentedA '13', '-1925,

UNITED .sra-TES;

PATENT oFFifcE.

IOBGAN' X. `ARMSTRONG, 0F WINNETKA, IiLINOIS, ASSIGNOR, BY MvEBNEASSIGN- HENTS, 10 THE BEAVER PRODUCTS COMPANY, INC., A CORPORATION Ol'YORK.

rLAs'rmi Bonnin.

appii'uon ma october 1, 1921. semi in. 504,155.

To all whom/t may cancer/n.:

Beit known that MORGAN K. ARMSTRONG, a citizen of the United States, anda resident of the city of-Winnetka, county of Cook, State of Illinois,has invented an Im rovement in Plaster Board, of which the ollow- .ingis a specification. p

This invention relates to composite board, known generallyl as plasterboard. Among other objects, t e invention is .intended to provideimproved boards having plaster receiving surfaces of uniformcharacteristics, wherebythe lastered or otherwise coated surfaces will eof uniform and improved quality` with a decreased' tendency to crack atthe joints between adjacent boards.

.Another object is to provide a board which will retain its .shape in aplaster w ceiling or analogous location.

The invention consists in the novel combinations and constructions to behereinafter described and claimed for carrying out lthe above statedobjects and such other objects as will appear from the description andclaims. y

The invention is illustrated in a preferred embodiment in theaccompanying drawing wherein: v

Fig. 1 is a fragmentary perspective view of a plaster wa l. employing acomposite board embodying features of this invention.

Fig. 2 is an enlarged section of a plaster boar A Like characters ofreference designate like parts in the several figures of the drawing. Inthe illustrative embodiment shown in the drawings,'the composite board10, comprises a substantially rigid body, or core 11, having coveringmaterial 12 on one or both faces thereof. TheV body 11 may be of anysuitable material such as plaster, to which the coveringmaterial 12 isadapted to adhere.

The covering material is preferably of a fibrous character, such asheavy paper which is manufactured or treated so as to retard for a givenperiod of time, the penetration and the faces of which of Water ormoisture,

laster or the like.

are adapted to adhere to Preferably the cover s plurality of plies, theouter plies, being unsized or adapted to adhere to or receive plaster,and the intermediate plies being ter body, may

' the plaster or eet is made of a.

treated or adapted to preventA the penetration of moisture through thesheet for a 66 given period'of time. For instance, in thev manufactureof a paper covering material, the outer ply or plies on the outside ofthe sheet and also if desired, the outerfply or plies on the inside ofthe'sheet next the' plaswhich isunsized or slack-sizec and th'eintermediate lies may be made from stock which is sized) to prevent'lthe penetration of moisture by a suitable sizing such as resin. The termslack-sized is used to characterize fibre stock which is 4treated by orcontains a compound which neutralizes any sizing which may exist in thestock and maintains the stock in unsized condition. The .number of pliesin the paper may be varied in order to provide a sheet of the requiredthickness and strength and inforder to provide unsized and sized plieslof suitable thickness and having the proper characteristics. Forinstance, it is desirable that the unsized outer layer be of sufficientthickness to properly and firmly retain or adhere to plaster or othercomposition em'- ployed. On the other hand, it is desirable that theunsized ply or plies, particularly those on the outside surface of theboard, be thin enough or their water-absorbing capaci- '.ty sufficientlylimited that they will not ab- .sorbtoo great a quantity of water as tointerfere with the cr stallization of the plaster. The interme iatesized ply or plies should be so sized that they will prevent thepenetration of any substantial quantity of moisture through the paperfor a length of time sufficient to permit the convenient handling of theboard during manufacture and to permit at least a partial setting ofthe-plaster core and, after the hoard is used, `to permit an adequatesetting or drying of other surfacing applied to the board.

In the illustrative form, shown in Fig.' 2, the covering material, whichhas been drawn on an exaggerated scale to illustrate its structure, is apaper sheet, composed of five be made from paper stock plies 13, 14, 15,16 and 17, the middle three,

nuinber of sized and unsized plies or the total number of plies in thepaper maybe varied to suit particular requirements.

In Fig. 1 is shown an illustrative Wall construction, employing a boardembodying the invention above described. The Wall comprises the) usualsupporting structure 18, to which the plaster hoard is nailed orotherwise secured. To the surface of the board is applied one or morelayers 19 of plaster or other surfacing in the usual manner. The firstcoat of plaster adheres to the unsized surface of the covering materialof the board, and the moisture retarding characteristics of theunderlayer of the covering sheet prevent any Water, particularly theWater of crystallization content, from being absorbed o-ut of theplaster surfacing into the paper and plaster core of the board. Thisinsures a uniform and simultaneous drying and setting of the plasterorother surfacing on adjacent boards and the consequent uniformcontraction of the plaster surfacing on adjacent boards.

The unsized outer layer of the covering sheet is so thin that even ifits Water-absorbing properties vary for different boards, this factorWill not appreciably interfere with the uniform setting and drying ofthe surfacing. But it is seldom possible to obtain Wholly unsizedpaperfor covering sheets which is sufliciently uniform in its effect upon theplastered surface that the plaster on adjacent boards Will act alike.The

' water-absorbing properties of and the speed at which water penetratesunsized coverino paper of this type, frequently vary to suoli an extentthat the plaster surface in one board will set and dry lon before thesurface on the adjacent boar has set. This causes uneven and irregularcontraction of the plastered surfaces and results in cracks at thejoints between the boards. Frequently the Water of crystallizationcontent in the plaster surface is partially absorbed by the paper andplaster core of the board, leaving the plaster surface chalky and Weakwhen it is dry.

The improved board may be used on ceilings and 1n similar situations andplastered over Without the danger of sagging. The Water from the plastercannot appreciably penetrate -the paper and enter the plaster core tosoften it and permit it to sag or Warp.

The illustrative plaster board may be made in any appropriate manner.For instance, a bottom cover-sheet may be led past a chute whichdeposits plaster thereon, after which a top sheet is placed upon theplaster and the board thus formed passed between a pair of rolls whichfirmly unite the cover sheets with the plaster. f desired the margins ofthe bottom sheet may be progressively folded up and over the margins ofthe top sheet as shown at 20, Fig. 1, a layer 21 of plaster beingemployed to firmly cement the folded margins in place. The provision ofa sizedv fpaper having unsized surfaces results in a rm bond between themargins of both sheets and the plaster layer 21.

As will appear to those skilled in the art, the invention is applicableto composite boards and the like made of materials which arefunctionally equivalent to, but specifically diferent from the plasterand paper referred to above. Obviously, the invention is not limited tothe particular embodiment illustrated but may be variously modified.Moreover, certain features may be advantageously employed in variouscombinations and subcombinations and need not all be ,used conjointly.

`l claim:

1. A composite board, comprising in combination a body of plaster o-rthe like and covering material adhering to the surface thereof, saidcovering material having both surfaces of a character to receive andadhere to substantial penetration of moisture therethrou h.

2L composite board comprisin in combination, a substantially rigid odyand covering material adhering thereto, said material having unsizedsurfaces and a sized center.

3. A composite board comprising, in combination, a substantially rigidbody and covering material adhering thereto, said covering materialhaving absorbent surfaces and a moisture retarding center.

4. A composite board comprising, in combination, a body of plaster orthe like and covering material therefor adapted to retard thepenetration of moisture throu hthe same, the inner and outer surfaces osaid material being adapted to adhere to plaster.

5. A com osite board comprising, 1n combination, a ody of laster or thelike, covering material there or consistin of a lurality of plies, anintermediate p y of w ich is sized, and the outer plies being adapted toadhere to plaster.

6. A composite board comprising, in combination, a body of plaster orthe like, a paper covering sheet therefor consisting of a plurality ofplies, the outer plies being unsized and an intermediate ply beingsized.

7 A composite board comprisin in combination, a body of plaster or thelike, paper coverin sheets therefor consisting of a plurality o plies,the plies at the exposed surface of the board being unsized and certaininner plies being sized.

8. 'A composite board comprising, in combination, a body of plaster orthe like, fibrous covering material therefor havin an` outside unsizedlayer and an inner sized layer.

9. A plaster board comprising in combif' i n 1,556,515

nation a plaster body; covering material adhering to said laster body,vsaid covering material being olded around the edges of said plaster bodyto envelopethe same, and having its margins arranged in overlappingrelation, the overlying margin being cemented in place by an interveninglayer of plaster; said overlapping margins being treated to retardmoisture penetration, but having their surfaces adjacent said layer ofplaster treated to cause them firmly to' adhere t0 said layer ofplaster.

10. A p-laster board, comprisinfv in combination, a plaster body;covering material adhering to said plaster body and treated to retardmoisture penetration; said covering material being folded around theedges of said plaster body to envelope uthe same and having its margins.arranged in overlapping relation, the overlying margin being cementedin place by an intervening layer of plaster; said margins having theirsurfaces adjacent said plaster layer unsized to cause said plaster layerto adhere firmly thereto.

l1. A plaster board, comprising in combination, a plaster body;lcovering material adhering to said plaster body, and covering v itsvfaces and reinforcing the same; said covering material having surfacesto which plaster readily adheres but treated to retard moisturepenetration.

In testimony whereof, I have signed my nameto this specification.

MORGAN K. ARMSTRONG.

